1. Field of the Invention
The present invention generally relates to an expansion device and, more particularly, to the improvement of an expansion device that is connected to a host device through a cable connection or a connector fitting and that expands the functions of the host device by transmitting a signal, which is read from a data recording medium, to the host device.
2. Description of the Related Art
Information processors such as portable computers, notebook personal computers (hereunder abbreviated to PCs), mobile PCs, laptop PCs, portable digital assistants, portable information processing devices, and portable terminals have become available. When such an information processor is carried by a user, a reduction in size and weight thereof is required. When used on a desk, such an information processor is required to have a wide range of functions. Thus, for example, the size and weight of the main body of a notebook PC must be reduced. Moreover, various expansion units, such as a CD-ROM drive, a floppy disk drive, and a DVD (digital versatile disk), which can be connected to or incorporated into the main body thereof, have been put into practical use.
However, for instance, a CD-ROM drive differs from a high capacity floppy disk drive in structure of a connector for connecting the main body of a notebook PC thereto. Because the notebook PC is downsized and has a small available area for connectors, it is impossible to install a large number of kinds of connectors thereon. Consequently, a limit to the number of kinds of connectors installed in the notebook PC results in a restriction on the kinds of expansion units that can be connected thereto.
Thus, in recent years, a bay unit serving as an expansion device to be used by being connected to a host device, such as the main body of an information device like a PC, has been being put to practical use. This bay unit is used by being connected through a connector to a host device that is an electronic device. Moreover, this bay unit has a main body provided with a slot called a bay. Recording/reproducing devices, for recording information on or reproducing information from data recording media and which have standardized sizes and output terminals, are inserted to this bay.
The recording/reproducing device to be inserted into the bay of the bay unit can be one of various devices, such as a device for recording information on and reproducing information from a static recording medium using flash memory, in addition to a disk drive, such as a CD-ROM drive, a DVD drive, a floppy disk drive, and an MO (magneto-optical) disk drive. This bay unit may be called “an expansion bay housing”, “a docking bay”, or “a multi-purpose bay”.
On the other hand, ordinary CD-ROM and DVD drives are enabled to reproduce data from an audio disk as well as from a data disk. Thus, audio signals to be reproduced as sounds of music can be processed. Consequently, the recording/reproducing device inserted into the bay of the bay unit can read audio signals from an audio disk. Further, the recording/reproducing devices each have a function of outputting analog audio signals in addition to a function of outputting digital data signals. Furthermore, the conventional bay unit can transmit either of a digital data signal and an analog audio signal, which are outputted from a recording/reproducing device, to a host device. The decoding of the digital data signal and the conversion of the analog audio signal are performed in the host device.
Thus, the conventional bay unit is used by being connected to the host device. Therefore, source power is supplied from the host device to the bay unit itself and the recording/reproducing device. There is no need for connecting a power supply to the bay unit. Consequently, when the power supply of the host device is turned off, the recording/reproducing device is simultaneously disabled.
Meanwhile, users of the bay unit demand that, when the power supply for the host device is turned off, the recording/reproducing device can still reproduce audio disk by using only the bay unit, so they can enjoy music recorded on an audio disk. However, in the case of using the conventional bay unit, the reproduction of an audio disk cannot be performed when the power supply for the host device is turned off. Moreover, users have demanded that they can enjoy music recorded on an audio disk by disconnecting the bay unit from the host device and using only the bay unit. The conventional bay unit, however, cannot be used when disconnected from the host device.